What Causes Milky White Cloudy Aquarium Water?

Guppies in the aquarium

Milky white cloudy aquarium water is often just temporary. Poorly rinsed gravel in a new aquarium can cause white cloudiness. Restarting the filters after a shutdown can cause debris and tiny air bubbles to create a white haze. Adding supplements such as bacteria, pH adjusters, or calcium can also create a temporary milky white haze in the water.

All of these sources of white cloudiness are usually just temporary, lasting only a few hours to a few days.

If the cloudiness persists, it is likely caused by bacteria growing at rates that turn the aquarium water milky white. This kind of fast bacteria growth is usually the result of excessive organic waste within the fish tank.

Causes for milky white aquarium water:

  • The aquarium is new and bacteria are settling. These nitrifying bacteria are needed as they make the water safe for fish by converting highly toxic ammonia to the less toxic nitrate (see ‘The Nitrogen Cycle‘ for more info). During the initial stages of a new aquarium setup bacteria and waste levels will not be balanced, often resulting in milky white cloudy aquarium water.
  • The bacteria colony has been disturbed by environmental changes i.e pH or temperature fluctuations or by anti-bacterial medication. Re-establishing of the colonies can cause the water to turn white.
  • Larger additions of fish or livestock can cause bacterial colonies to multiply every 20 minutes in an effort to convert the additional organic waste being produced. The re-balancing of the biological balance will require some time. Again the result can be milky white cloudiness.

With growing bacteria in the aquarium, oxygen can be depleted. To solve the problem, correct any of the above mentioned causes. Most common are the addition of livestock which causes dangerous spikes on organic waste.

Algone will clear and prevent cloudy water by removing organic and inorganic waste. Algone will also minimize ammonia and nitrite spikes and lessen their highly toxic effect on fish and other livestock.

Check out Algone here

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my water goes cloudy every time I feed my fish I am using Tetra Crisp


It can happen if the aquarium is not yet fully cycled, or if the aquarium is overstocked, or if too much food is used. In essence, it is likely a bacteria bloom. You can try to reduce the amount of food to see if that make the difference.


hi, i took control of my friends fish tank which is a 20 gal and he had 5 peacocks cichlids in it. i know for a fact that its over crowded and unfortunately i don’t have room for a bigger tank in my apartment at this time. i don’t want to get rid of the fish i want to keep them. how do i control the cloudy water in the tank.


There are preventative measures, such a feeding very lightly, and religiously following good maintenance practices. Water changes, vacuuming the gravel etc. Using polyester filter fibers will help in the process. Place the fibers in the filter and remove frequently (once a week).


Thank you for your help and your time. I vacuum out the gravel and and Did a water Chan last night and it helped a lot and now I will use the filter fibers too thank you again


Hi, my tank is a small 6.8 gallon tank, decorations and stones, which both I got from a family member who used them about 10 years ago. I recently set this tank up with the filter, air pump, decorations/stones and fish and the water was clear and fine but now the water has turned very cloudy which has me on edge for the fish, as this is my first time in doing this. I feed the fish flakes about 2 times a day as recommended by an employee at a fish place. If I do need to clean the tank… Read more »


Don’t feed the fish but once a day and only as much as they can consume in a few min. Start out with a small pinch and go from there. You can always add more, but you can’t take away. Look for a tank vacuum and I recommend looking up tank videos for beginners on YouTube. I’ve been doing this for a while and I learn new stuff every time. Make sure to read the comments of the videos before implementing anything as if there is anything dangerous or wrong with what the video suggests then fellow you tubers will… Read more »

hi I been going now for a few months my temp was 74-76 so I wasn’t happy with it I turned it up to 78-80 I also speeded my pump up so the water was breaking up at the top now my water is a bit misty


How do I treat cloudy well aquarium water? I have had it set up for a couple months and I’m keeping Koi in a 125 gallon aquarium. I was told by Pet Supplies Plus to use Stress Zyme to add bacteria to uncloud and it’s been a week since I used it and the aquarium is still cloudy.


If the cloudiness comes from the well water, you should check the system and filters. If the aquarium is cloudy than this is due to either overstocking, or overfeeding. The cloudiness is bacteria growing at rapid speeds, actually pretty much the ones you keep adding through Stress Zyme. You can discontinue SZ and focus on correcting stocking and feeding habits. Algone will certainly help to speed up these efforts.


It could be your hot water heater. Run hot water from your faucet into a clear glass and if it’s murky or cloudy the problem is your hot water heater. Discovered this after tearing out my hair trying to solve the problem of cloudy water in my tanks.

Paul chaunt

I just setup a freshwater tank for tropical fish possibly chiclids I have crush coral for gravel it’s 39 gallons and big enough filter it’s white milky cloudy water now I read I possibly didn’t rinse gravel enough should I put in something for the cloudy water if so what or should I let the filter keep running to see if it clears thank you Paul

Since it’s a newly set up aquarium, it’s likely just fine dirt particles from the gravel. The filter should pick it up and clear it within a day, give or take.


I have a 100 gallon tank set up and it contains 2 Oscars and a Pleco. I have had this tank set up for about 5 months and have had no issues except the Ph is having issues staying at 7. Most of the time it is about 6. But about 8 days ago my tank started getting cloudy and milky looking……I changed out 25% of water…..and it started to clear up…slowly….then a few days ago I came home and it was getting very cloudy again…As of today it is extremely cloudy….tank is 18″ wide and it was so bad… Read more »


The pH plays a major role in this issue, because the bacteria converting waste to ammonia/ nitrite/ nitrate (beneficial bacteria) will be severely inhibited in their function starting at a pH of 6.5
With lower pH levels especially 6 and lower, the bacteria will cease their function altogether. Once the pH goes up again, a bacteria bloom can occur. as the bacteria try to re-establish the colonies. It is that bacteria bloom that turns the water milky white.
First things first, fix the pH problem. We have a great overview including actual cases from hobbyists listed on https://www.algone.com/adjust-ph-aquarium

kathleen Sanders

Less feeding will bring your water back to normal I’ve had fish for 25y


i recently bought a 75 gallon aquarium. i filled the tank yesterday and today ist too cloudy. i added aquarium salt and white marvel chips. is it due to adding of those chips or nitrogen cycle process? can you help?

Since the tank was just set up, this is likely just substrate particles floating in the water. The filter should remove these and clear the water in just a day or two.


Hi i have a 20 gallon tank for two aquatic frogs thag I just cleaned a few days ago, washed the rocks and rinsed off the little log and plant I have it there. The first day it looked clean and clear but now (the third day) the water looks foggy and milky like it is dirty again already. This is the second time I have cleaned this tank and the first time I cleaned it, it did not look like this. The tank was clear for about three weeks so that is why I am worried that it is… Read more »


If you clean the aquarium too thoroughly, you wipe out the bacteria needed for the aquarium to provide a healthy and safe environment for the fish/ frogs. In essence, you are cycling the aquarium over and over. Here is a good maintenance plan that should make things much easier: https://www.algone.com/aquarium-maintenance-tips-and-fish-care-guidelines

Valerie Martin

My tank water is lime green and the water is making my bedroom smell really bad. Its the water in the tank what should I do

This is quite vague, so in a nutshell… make sure you are: 1. running an adequately sized aquarium filter 2. performing regular water changes 3. not overcrowding the aquarium with too many fish 4. not overfeeding your fish The green water is likely free-floating algae. Algae thrives in high nutrient water, particularly high nitrates. Nitrates are the result of decaying waste in the fish tank… uneaten fish food, fish poop, etc… Accumulating nitrates are due to too much waste entering the tank, a lack of maintenance, or both. Good aquarium maintenance practices are essential for a healthy aquarium, as are… Read more »

Mark P

We moved my fish tank downstairs and cleaned it out and everything got a new filter rinsed the rocks and everything and then the water got white and cloudy so we cleaned it again and it happened again. Not sure what’s happening


That would be a bacteria bloom. Bacteria, which make the water safe for the fish, settle anywhere in the aquarium. The filter is a preferred location because of, among others, the higher oxygen supply. Replacing the filter will also displace the bacteria. Cleaning has the same effect. If you see a slimy area, that is the protective coat of the colony. Just rinse the filter if it needs cleaned. Adjust the filter outlet, or lower the water level to the point where the filter outlet creates waves. This will ensure proper oxygen levels. You can wait this out, or use… Read more »


Hello I have a five gallon tank that I am setting up for a betta. I thought I washed everything thoroughly before putting my water in with my betta water conditioner. It got cloudy about two days in, and now has been cloudy for 3 days. I have a filter, heater, gravel, and a digital thermometer in it so far, haven’t put decorations in it yet. What should I do? Should I wait it out or just restart?


Some conditioners can cloud the water especially if they claim to have bacteria in the mix. You can wait this one out and read up on the following in the mean time.

Krystian Borja

Hi i have a 15 gallon aquarium it has not been cycled and i added new fish. The fish for what i see is ok and it is eating. But the water is cloudy. What should i do?

Just feed sparingly and perform a modest water change of about 15% of water every 5 – 7 days. This should keep nutrients lower and ease the effects of the aquarium break-in on your fish. Once sufficient beneficial bacteria are established, the tank should clear up on its own. Otherwise, consider an aquarium water clarifier such as Algone.

Guy Hanna

I have a brand new 65 gallon Aquarium. I rinsed off my gravel and set everything up for my fish. It is still foggy white, Is it my gravel or just that it is new?

Yes, it’s likely just from the gravel. If it persists for more the a couple of days, it may be a bacterial bloom. One post below, Thilo explains this to another aquarium keeper as follows: Bacteria that grow ahead of the beneficial bacteria can grow at speeds that turns the water cloudy. This is referred to as a bacteria bloom. No danger for as long as the aquarium is well oxygenated, as most are just by water surface movement. Bacteria blooms can occur if, the aquarium is newly set up, fish have been added, the bacteria got disturbed by either… Read more »


I have a 54 gallon tank. It’s been set up for bout 3months now. I decided to do a GLOW FISH TANK. It was touch and go for awhile …getting the water just right. Anyhow I have been able to add fish over time but now my water is very cloudy…took the water to have it checked and all was good except the ph was a little acidic but said not dangerous so we put the ph adjuster in it…please help ,,,do I just let it run it’s course….

Bacteria that grow ahead of the beneficial bacteria can grow at speeds that turns the water cloudy. This is referred to as a bacteria bloom. No danger for as long as the aquarium is well oxygenated, as most are just by water surface movement.
Bacteria blooms can occur if, the aquarium is newly set up, fish have been added, the bacteria got disturbed by either to intense cleaning, filter changes, changes in live stock, or medication (antibiotics). You can use Algone to speed up the process of clearing the water, or wait it out.


I have a 30 gallon tank i recently did my yearly full clean of the tank and cleaned the rocks its murky white, and its getting worse. The water is more white after a fewe days.

This sounds like a bacterial bloom, which is not uncommon for newly setup aquariums. Since you did a full cleaning, your tank will have to re-cycle, and you may experience what’s called New Tank Syndrome.

In any case, feed sparingly and avoid any big water changes. Your tank needs a chance to balance and any big changes will only delay that balancing. With time, the water should clear up on its own. If the problem persists, add Algone to your filter.

debbie hollis

Hi the water in the fish tank was a brown colour and smelly what was wrong with the water

That may indicate you are experiencing an algae bloom.

Read more here:

Description of Common Aquarium Algae
Aquarium Algae Control
Nitrate Control is Algae Control

Ayush sinha

I have made a 20 gallon aquarium before 2 days ago and yesterday when I added water to my aquarium the water remains cloudy. I have very less amount of gravels they are unclear. I have cleared the gravel but water remains hazy and I have only 2 fish, one red cap and koi carf, they also have produced lots of waste in this new aquarium. Please help me to remove cloudy water.

The cloudy aquarium water is likely just particles from the gravel that haven’t yet settled, or you are already experiencing a bacterial bloom. A bacterial bloom is caused by an imbalance of nitrifying bacteria in the fish tank. This is not unusual for a new aquarium. Avoid any big changes such as large water changes, or the addition of any new fish at this time. This should clear up as the aquarium establishes a healthy biological balance. Also see ‘New Tank Syndrome‘ for more information.


This changes has Influence in my red cherry shrimp tank. Temperature, Ph and hardness is good for these Nitrate & Ammonia is low but i dont konw what happend in my tank 🤔

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